As disclosed in A. N. Pudovik, Chemistry of Organophosphorus Compounds, MIR Publishers (Moscow), 1989, pp. 68-92, it is known that organophosphorus compounds, such as phosphites and phosphonites, have a tendency to hydrolyze when exposed to moisture, that they can also be decomposed by a transesterification reaction when crystallized from alcohols, that these decomposition reactions are catalyzed by acids, but that the removal of trace amounts of acid impurities from the organophosphorus compounds is very time consuming and expensive.
U.S. Pat. No. 4,402,858 (Capolupo et al.) teaches that the hydrolysis of neat phosphites, i.e., phosphites already recovered from their synthesis reaction mixtures, can be minimized by blending them with certain metal carboxylates so as to provide phosphorus/metal atomic ratios of 78-900/1 in the blends. European Patent Application 0 400 454 (Enlow et al.) teaches that hydrolytic stability can be imparted to neat organophosphites by blending them with 50-200%, based on the weight of the organophosphite, of a metal soap, a metal oxide, or an alkali metal salt of an inorganic acid and optionally also with an inert support.
Although there is considerable value to minimizing decomposition of an organophosphorus compound after it has been prepared, e.g., during storage or during utilization in an end-use application, such as the stabilization of polymers and other materials, it has been found that decomposition--sometimes extensive decomposition--can occur even before the organophosphorus compound is recovered from its synthesis reaction mixture, even under anhydrous or substantially anhydrous conditions, but especially when alcoholic solvents are used in the crystallization.
It is advantageous, i.e., both simple and inexpensive, to recover organophosphorus compounds by crystallization from alcohols. However, the nature of alcohols is such that they promote decomposition of the organophosphorus compounds both by reacting with the compounds themselves and by containing water which can also react with the compounds. These reactions lead to lower product yields and increase the formation of impurities.
The acid-catalyzed decomposition of organophosphorus compounds during recovery from its synthesis reaction mixture is a problem, not only because of its reducing the yield of the desired product, but because the impurities contributed by the decomposition can prevent the organophosphorus compound product from being usefully employed in some applications. However, as already indicated, removal of the trace amounts of acid impurities that catalyze the decomposition is too time consuming and expensive to be a satisfactory solution to the problem, especially when the organophosphorus compounds are prepared on a production scale.